Water Conservation Through HVAC Technology

Water Conservation Through HVAC Technology

Headlines out of Cape Town, South Africa, this year made clear that sustainability isn’t only about saving electricity or the fuels often associated with power generation. It is difficult to imagine a city running out of water, but it’s no longer impossible. Water conservation is getting more important in the U.S., and HVAC systems on a large scale represent a chance to make an impact (or not).
It’s good news, then, that the wider realm of HVAC energy efficiency provides the chance to conserve water both near and far.

COST AWARENESS
More directly, when availability tightens at all, environmental impulses in the commercial sector often get a nudge from a most traditional area of concern: profit margin.

“We’re also seeing a shift in some markets and applications toward air-cooled chillers, especially where applications can use higher chilled water temperatures, such as data centers,” he said. “Absorption heat pumps using waste heat are another area of growth.”

Attitudes and levels of interest can be as important as the equipment itself. Ian Dempster is a senior director of product innovation at Optimum Energy and a certified energy manager. Optimum sells many of its optimization projects on a return on investment (ROI)-basis, so the attention to what customers will get for their efforts is constant.

“Most customers want to understand exactly what those savings and efficiencies will gain them,” Dempster said. “That taught us to focus and refine our facility energy modeling tools and to train our engineers to be very accurate in producing baselines, along with projected baselines that show, in almost real time, how well the products are performing. Customers really like being able to look at a screen on their computer, or an app on their smartphone, and see how much their facility is saving in energy, dollars, CO2, and water.”

WHERE ARE THE OPPORTUNITIES?

Dempster sees well-selected equipment upgrades and using optimization software as the two largest opportunities. He described an older building where a secondary/primary pumping gets converted to variable primary.

“Effectively getting rid of the second set of pumps and performing some piping rework, the savings can be phenomenal,” he said.

Team that with replacing decades-old chillers or boilers, and customers can gain anywhere from 15 to 35 percent efficiency improvements for that system, which will translate to less water use, Dempster added.

OFF THE SHELF AND ON THE CASE

“We are making use of the mountains of data we have collected over the past 12 years that show how HVAC systems and equipment respond to differing conditions,” Dempster said. “Using this information, we created three modules that use machine learning to gain intelligence over time and make actionable decisions that gain even further results. To date, we have seen these modules deliver 5 to 7 percent additional savings above the typical optimization savings of 30 percent.”

MICRO TO MACRO

Dempster promotes holistic control here, but with a lesson about unintended consequences when it comes to deploying seemingly beneficial measures like adjusting chiller supply temps.

“This is a very good strategy with proven results,” he said, “but if the temperature is raised too high, all savings may be lost.”

Why?

“Because as AHU [air-handling unit] fans ramp up to provide more air to the building, they are not cooling the air enough,” Dempster said. “Controlling the system holistically prevents this type of scenario.”

DRIFTING IN THE RIGHT DIRECTION

Talking to building owners directly for over 16 years about optimizing chillers has let Dempster see an evolution in attitudes regarding the bigger efficiency equation.

“One of the large concerns we consistently ran into many years ago was the worry that installing VFDs on electric motors would decrease the motors’ life span and create problems,” he said.
Now, of course, it is readily accepted that VFDs, in tandem with optimization strategies, can make a real difference. However, misconceptions remain.

“Contrary to standard belief, using less equipment is not a guarantee of reduced water consumption and better energy savings,” Dempster said. “Operating two or more units of modern variable equipment (such as cooling towers or chillers) at reduced speed and load oftentimes allows the machines to operate at lower temperatures.

“This can save more energy than having one of those pieces operating at close to full speed and load,” he added.

Just when more building owners are getting used to thinking about water efficiency, it turns out that the best approaches might require thinking twice.